The present invention relates to a light wave conductor-sensor for tension. More particularly it relates to such a light wave conductor-sensor which has a primary coated light wave conductor, a tension-proof casing of a fiber-reinforced synthetic plastic material, and an inhomogenous synthetic plastic layer arranged between them. It is embedded into structural parts to be monitored and allows an article monitoring of the structural parts as to their mechanical stresses, such as tension, breakage and bending. The invention also relates to a method of manufacturing of such a light wave conductor-sensor.
It is known to embed a light wave conductor in a tension-proof wire of a fiber-reinforced resin structure and to monitor the wire by means of the light wave conductor as to tension, breakage or bending, as disclosed for example in the DE-OS 3,350,234. For this purpose the light wave conductor is enclosed by a synthetic plastic layer which has an inhomogenous structure. The light wave conductor, the intermediate layer and the wire are fixedly connected with one another mechanically over their entire length. The light wave conductor is provided at its both ends with connections for a light continuous-check device. The intermediate layer between the light wave conductor and the tension-proof casing is composed of synthetic plastic or synthetic resin with fine-grain powder of glass, quartz, corundum or abrasive added thereto. In accordance with a further embodiment, the intermediate layer can also be composed of resin-impregnated glass fibers which are wound around the light wave conductor. Such a tension-proof wire with an embedded light wave conductor must be used in a respective thickness with an outer diameter of over 5 mm as monitorable reinforced concrete wire. Its design can still be improved in the sense of the sensor sensitivity.
In this tension-proof wire the casing of the light wave conductor core is composed of a fiber-reinforced resin structure, for example of glass fibers in a matrix of polyester resin. It is also known in fiber-composite materials to embed the reinforcing fibers (instead of a matrix of synthetic resin in the sense of hardenable duroplastic synthetic plastics), in a matrix of thermoplastic synthetic plastic materials, preferable examples are: for glass fibers to use polyamide as a matrix, and for fibers of carbon or aramides to use high density polyethylene, polypropylene or polyvinylidenefluoride.
It is also known to manufacture shaped members of glass-reinforced synthetic plastic material by means of horizontally operating drawing processes. In accordance with this technique a number of glass fiber strands (rovings) is drawn from a coil frame, impregnated with resin, and guided through at least one drawing nozzle. The compression takes place in the nozzle, and moreover resin excess and air are removed. After this, the fiber-reinforced shape member is hardened in several furnaces, cooled again in a bath, and after discharging from the drawing arrangement is subdivided into individual pieces.